The present invention relates to a method and apparatus for cleaning rails by removing contaminants such as leaves, lubricating oil, fuel oil, grease, water and ice coated onto the rails. The invention has a particular application in cleaning the rails of a rail system. The term xe2x80x9crail systemxe2x80x9d as used herein encompasses all systems in which wheeled vehicles travel on rails, and in particular railway systems for trains, and tramway, plateway and monorail systems and similar systems.
It is known that, due to the movement of trains in a railway system adjacent to piles of leaves, appreciable amounts of the leaves may be transferred to the top surfaces of the rails and, once there, are compacted by the wheels of the trains into a hard coating on the tops of the rails. Further, lubricating oil, fuel oil and grease may be transferred from the trains to the rails, and water and ice may form on the rails by precipitation from the atmosphere or otherwise to form softer coatings. The term xe2x80x9ctrainxe2x80x9d as used herein encompasses all forms of railway rolling stock, trams, monorail rolling stock and all vehicles design to travel on rails.
The presence of the hard coating of contaminants such as leaves or the softer coating of contaminants such as lubricating oil, fuel oil, grease, water or ice has two important effects. Firstly, it decreases the traction between the driving wheels of the trains and the rails and, secondly, it forms an electrically insulating layer which prevents continuous electrical connection between the wheels of the train and the rails.
It is known to use special electrical apparatus which continuously detects the positions of trains in a railway system and sends signals to a control centre so that the position of each train in the railway system can be indicated on a display board in the control centre. The correct operation of the special electrical apparatus depends on the establishment and the maintenance of a continuous electrically conducting path between at least some of the wheels of each train and the rails. The presence of a hard or soft coating of contaminants as described above on the tops of the rails destroys this electrically conducting path and prevents the correct operation of the special electrical apparatus which indicates the position of each train in the railway system.
From a safety point of view it is essential that the position of each train in a railway system should be known all the time to ensure that signals are set correctly, that a train does not appear to pass through a danger signal, that each train is in the correct position in the railway system and that two or more trains arc not on a collision course. It is therefore very important that the above described special electrical apparatus operates continuously to provide all the above information about each train.
It is known to try to remove contaminants of the above type. Various methods and apparatus have been used and proposed, including mechanical devices and processes and chemical devices and processes. These devices and processes are not always effective to remove or destroy the contaminants and operate only relatively slowly. Therefore, if a device or process of these types is incorporated into a train moving along the rails which are covered with the contaminants the train can only travel slowly. Performing the operation at this speed of movement severely holds up passenger and freight trains which cannot move until the contaminants have been completely removed from the rails.
The above problems due to contaminants on the surfaces of the rails of railway systems occur also in tramways, plateways and monorail systems and similar systems.
Patent Specification DE 43 23 700 (Document D1) describes the use of a laser beam to xe2x80x9cevaporatexe2x80x9d a layer of a contaminant such as water, snow, ice etc. on a metal substrate such is a rail and to remove the vapour by a jet of air etc. The temperature to which the contaminant is raised is not specified.
Patent Specification U.S. Pat. No. 4,063,063 (Document D2) describes the use of a laser beam to xe2x80x9clooserxe2x80x9d a hard layer of contaminant such as an oxide on a metal substrate. The loosened contaminant is then removed from the substrate by a mechanical or a chemical process.
Patent Specification DE 195 42 872 (Document D3) describes the use of a laser beam to detect a contaminant such as oil or water on a substrate. The laser beam is not used to remove or destroy the detected contaminant.
The object of the present invention is to provide an improved method and apparatus for cleaning the rails of a rail system by removing contaminants on the surfaces of the rails, preferably at a speed close to or at the normal speeds of the vehicles travelling on the particular rail system being treated.
According to one aspect of the present invention a method of cleaning a rail by removing contaminants from the surface of the rail comprises generating a high intensity pulsed laser beam and directing the laser beam onto the surface of the rail so as to destroy at least part of tho contaminants.
The temperature of the contaminants may be raised to at least 6000 degrees Celsius.
According to another aspect of the invention apparatus for cleaning a rail by removing contaminants from the surface of the rail comprises means for generating a high intensity pulsed laser beam and for directing the laser beam onto the surface of the rail so as to destroy at least part of the contaminants.
By using a high intensity pulsed laser beam which converts the contaminants directly into gases the destruction of the contaminants takes place very quickly. If the rail is part of a rail system on which vehicles run, the laser beam generating system may be mounted on one of the vehicles and operated while the vehicle is running. Since the destruction of the contaminants takes place quickly, it is expected that the vehicle can be run at normal speeds while the destruction process takes place.
If the contaminants extend as a coating on the surface of the rail the laser beam may be directed successively al different parts of the coating to result in the gradual destruction of all the coating.
The laser beam may alternatively be moved gradually along the rail, either to divide the coating gradually into two portions or to destroy all parts of the coating gradually.
The apparatus may include a shield to prevent the laser beam from being directed or reflected away from the surface of the rail. This will prevent the laser beam striking on any other surface spaced from the rail, in particular parts of a human body or an animal such as the eyes or anything else which would be damaged by the laser beam.